《嵌入式 Linux 系统的电源管理》讲义.ppt

Thesuccess sroad CELinuxPM WhatWe llTalk PMTheoryandHardwareSupport2 6kernelPM SubsystemCELFPMSpecificationAppendixCurrentPMImplementation Hardwarecomponents Hardwarecomponents PowerControlledComponentsinclude IntelPXAXscaleCPU real timeclock DRAM Flash LCD frontlight UART audiocodec touchscreen keysandpowerbutton etc TheXscalePXA27XCPUsupportsseveralpower savingfeatures XscaleCPUPMFeatures PXA27XPMfeatures includingfrequencyscalingandCPUcorevoltagescaling Andseveralmodesofoperation RunmodeAllpowersuppliesenabled allclocksrunningandeveryon chipresourceisfunctional IdlemodeCPUclockstopped otheron chipresourcesareactive Whenaninterruptoccurs theCPUisreactivated SleepmodePowerisswitchedofftothemajorityoftheprocessor Somepreprogrammedevent suchasapowerbuttonpress wakesuptheCPUfromthismode HandheldEnergyBudgets PMTheory OSPMfocusesonactivepowerconsumptionModulatemethods Voltage clockmodulateClockselectedPowersupplyselected KernelPM Subsystem KernelPM Subsystem WhatwewilltalkCoversthetwobroadareasofpowermanagement SystemPowerManagement SPM DevicePowerManagement DPM Andmore DevicePowerManagement DPM DevicePMDealswiththeprocessofplacingindividualdevicesintolow powerstateswhilethesystemisrunning Invokedexplicitlyondevices ormayhappenautomaticallyafteradevicehasbeenidleforasetofamountoftime SystemPowerManagement SPM SystemPMTheentiresystemisplacedintoalow powerstate runningsystemissavedbeforepowereddown andrestoredoncethesystemhasregainedpower Automaticallyenteralow powerstateafterithasbeenidleforsomeamountoftime orwhensomecriticalstatehasbeenreached Alsopolicydecisionsthatareuptotheusertoconfigureandrequiresomeglobalmechanismforcontrolling DevicePowerManagement Newdrivermodel LDM inthe2 6kernel whichprovidesahierarchicalrepresentationofthedevicesinthesystem Devicepowerstatesaredescribedas D states andconsistofstatesD0 D3 inclusive InfluencedbyACPISpec DevicePMDataStructs Adevice sPMinforstoredinstructdevice pm structdevicecontainsadevice pmobject structdevice pm dev power tpower state u8 saved state atomic tdepend atomic tdisable structkobjectkobj DevicePMDataStructs typedefenum DEVICE PM ON DEVICE PM INT1 DEVICE PM INT2 DEVICE PM OFF DEVICE PM UNKNOWN Device sinitialpowerstate dev power t enum SUSPEND SAVE STATE SUSPEND POWER DOWN enum RESUME POWER ON RESUME RESTORE STATE PowerDependencies TwostepstosuspenddeviceonetosavestateanothertopowerthedevicedownConversely onecallismadetotheresume methodtopowerthedeviceupanothertorestoredevicestate allchildrendevicesmustbepowereddownbeforetheirparentcanbepowereddown Conversely theparentdevicemustbepoweredupbeforeanychildrendevicesmaybeaccessed Onlywhenadevice sdependcount structdevice pm dependfield is0mayitbepowereddown intdevice pm get put structdevice RegisterPMhandlers staticint initi2c init void retval bus register DeviceSpecifieddriver explainlater RegisterPMhandlers staticstructdevice driveri2c adapter driver name i2c adapter bus RegisterPMhandlers staticstructdevice driveri2c pxa driver name pxa2xx i2c bus RegisterPMhandlers staticinti2c pxa controller suspend structdevice dev u32state u32level ifdefCONFIG PMi2c pxa wait bus not busy i2c pxa stop endifreturn0 InternalSequenceofDevicePM echon sys bus i2c devices 1 1 power state ncanbe 0 3 Whenn 0 resumestepssimilar state store drivers base power sysfs c dpm runtime suspend drivers base power runtime c suspend device drivers base power suspend c callsuspendhandlerofthebuswhichthespecifieddevicebelongsto callsuspendhandlerforthespecifieddevice SystemPowerManagement PowerStates KernelsupportsstatesareStandby Suspend andHibernate typedefenum POWER ON 0 POWER STANDBY 0 x01 POWER SUSPEND 0 x02 POWER HIBERNATE 0 x04 pm system state t SystemPMStates Standbylow latencypoweras power onsuspend systemconservespowerbyplacingtheCPUinahaltstateandthedevicesintheD1state Thepowersavingsarenotsignificant buttheresponselatencyisminimal SuspendAs suspend to RAM alldevicesareplacedintheD3stateandtheentiresystem exceptmainmemory isexpectedtolosepower Memoryisplacedinself refreshmode soitscontentsarenotlost ResponselatencyishigherthanStandby Hibernateconservesthemostpowerbyturningofftheentiresystem aftersavingstatetoapersistentmedium Alldevicesarepoweredoffunconditionally Theresponselatencyisthehighest Butwewon ttalkaboutithere SystemPMDataStructs structpm state structpm driver drv handlethepowerstatepm system state tsys low levelpowerstatesystemwillenterpm device state tdev lowestpowerstatedevicesmayenter structkobjectkobj objectformanaginganinstance slifetime structpm statepm state standby structpm statepm state suspend structpm statepm state hibernate SPMsysfsinterface Example cat sys power stateResults standbysuspendhibernate echosuspend sys power stateBywritingthenameofastatetothisfile thesystemwillperformapowerstatetransition SPMPlatformDrivers structpm driver u32states int prepare u32state int save u32state int sleep u32state int restore u32state int cleanup u32state structkobjectkobj intpm driver register structpm driver voidpm driver unregister structpm driver SPMPlatformDrivers structpm attribute structattributeattr ssize t show structpm driver char ssize t store structpm driver constchar size t intpm attribute create structpm driver structpm attribute voidpm attribute remove structpm driver structpm attribute pm attribute store methodwillcall enter state state andenterrelatedpmstate PowerStateTransitions Triggeredbywritingtherequestedstatetothesysfsfile sys power state Suspendsequence Firstverifythatthesystemcanenterthepowerstate PMcorethenqueststherunningsystembydisablingpreemptionand freezing allprocesses Next device suspend tosavesystemdevicestate driver ssave methodtosavelow levelsystemstate PMcorethendisablesinterruptsandcallsdevice power down toplaceeachdeviceinthespecifiedlowpowerstate Finally itcallsthedriver ssleep methodtotransitionthesystemtothelow powerstate PowerStateTransitions ResumesequencePlatformreturningexcecutiontothecorrectplace afterthereturnfromthedriver ssleep method PMcorepoweronalldevicesandrestoreinterrupts driver srestore methodiscalledtorestorelow levelsystemstate anddevice pm resume iscalledtorestoredevicecontext Finally thedriver scleanup methodiscalled processesare thawed andpreemptionisreenabled InternalSequenceofSystemPM echo standby sys power statestate store kernel power main c enter state kernel power main c ThisistheentrancetoSPM gowiththesameroutewhenpm suspend called InternalSequenceofSystemPM pm suspend callflowenter state kernel power main c suspend prepare kernel power main c pm prepare console kernel power console c freeze processes kernel power process c pm ops prepare device suspend driver base power suspend c suspend device foreachdeviceonthe dpm active list driver base power suspend c movetheentryfrom dpm active to dpm off or dpm off irq onsuspendhandlerreturns EAGAINsuspend enter kernel power main c local irq save Con InternalSequenceofSystemPM device power down drivers base power suspend c suspend device foreachdeviceonthe dpm off irq list drivers base power suspend c sysdev suspend drivers base sys c pm ops enter Systemwilldownheredevice power up calledwith irqoff drivers base power resume c sysdev resume drivers base sys c dpm power up drivers base power resume c resume device foreachdeviceonthe dpm off irq list driver base power suspend c movetheentryfrom dpm irq off to dpm active local irq restore suspend finish kernel power main c InternalSequenceofSystemPM device resume calledwith irqon drivers base power resume c dpm resume drivers base power resume c resume device foreachdeviceonthe dpm off list movetheentryto dpm active from dpm off pm ops finish targetPMspecificthaw processes kernel power process c pm restore console kernel power console c InternalSequenceofSystemPM suspend device drivers base power suspend c callsuspendhandlerthebuswhichthespecifieddevicebelongsto callsuspendhandlerforthespecifieddevicesysdev suspend drivers base sys c foreachkernelsusbsysandclasscallsuspendhandlerforeachdriveron global drivers registeredwithsysdev register callasuspendhandlerforeachdriverundertheclass callasuspendhandlerfortheclass InternalSequenceofSystemPM sysdev resume drivers base sys c foreachkernelsusbsysandclasscallaresumehandlerfortheclasscallaresumehandlerforeachdriverundertheclass callresumehandlerforeachdriveron global drivers registeredwithsysdev register resume device drivers base power resume c callresumehandlerofthebuswhichthespecifieddevicebelongsto callresumehandlerforthespecifieddevice PM OPS staticstructpm opsacpi pm ops prepare acpi pm prepare enter acpi pm enter finish acpi pm finish drivers acpi sleep main c pm set ops Thegloblestructpm ops pm opsislinktoacpi pm ops SothePMSubsystemcanbeusedwithACPIImplement PXAPM OPS PXAPM OPSImplementationpm set ops implementsuspendtoram AllthePMfunctioncanbeaccessedbysysfsinterfaces orapmd orothersD CELFPMSpecificationAppendix CELFspecifiedPMtechnologiesareclassifiedintothreecategories platformsuspend resume TalkedAbove devicepowermanagement TalkedAbove platformdynamicpowermanagement WillTalk Dynamicpowermanagementisusedforreducingpowerdissipationwhileaproductisbeingused Dynamicpowermanagementcoversalsoreducingpowerforveryshortidleperiodsoftimewhileaproductisbusy Andmore Dynamicpowermanagement Dynamicpowermanagement Socalled DynamicPM Suchpowermanagementcaninvolvedynamiccontrolofperipheralclocksandpowersupplies varyingthetimertickfrequencyduringidleperiodsandCPUfrequency voltagescaling Thisusesacombinationofuser spaceandkernel spacesoftwareaPolicyManagercomponentrunninginuser spaceaPowerManagementEngine PM Engine componentrunninginkernel space Dynamicpowermanagement Thesoftwareselectsthesystemoperatingstatebasedonacombinationofthefollowing applicationrequirementstheparametersforbatterylifetimeortaskdeadlinesCPUloadingthecurrentdeviceconstraintsthecurrentoperatingstateuserinteraction KernelPM Subsystem DynamicPMImplement DPM PowerManagementPolicy PoliciestellDPMhowtorespondtosystemeventsandlower raisethepowerusageaccordinglyPolicyisbasedonthefollowingsystemdependentterms OperatingPoints UniqueprocessorpowerstatesdefinedbytheadjustablepowerparametersforyoursystemOperatingStates CPUexecutionstates suchasSleep Task andIdle thataretriggeredbyanoperatingpointClasses Associateoperatingpointswithoperatingstates allowingyoutoassignanoperatingstatemorethanoneoperatingpoint UsingDPM OperatingStates DPMProvidestheseoperatingstates SleepIdleTaskIfmorearerequired definetheminyourarch specificDPMfileFilenamewillbeasfollowsdependingonyourarchitecture linux include asm arm arch dpm hlinux include arch ppc platforms dpm h UsingDPM Initialize bi